This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
It is generally known to provide a hand-operated cutting tool for use in pruning or trimming branches and the like, such as a lopper having a pair of pivoting members such as handles that actuate cutting jaws that cooperate to capture and sever a branch between the jaws. Such known loppers typically include a pair of handles pivotally movable between an open and closed position for actuating the cutting jaws between a full open and closed position. The known loppers may also devices intended to increase the available leverage provided by the handles, including levers and/or gears that transmit and increase a force from the handles to the jaws.
As a lopper cuts through an object (e.g. a roughly cylindrical sample of a wood material), the force required to cut increases up to a maximum, at a location approximately 60% through the sample, then decreases at a generally similar rate until approximately 90-95% through the sample where the force required to complete the cutting operation rapidly decreases. Typical cutting tools such as a lopper are sized such that with the tool fully opened, the average human holds the handles with arms abducted and elbows facing outward, and move with a transverse flexion of the arms until the tool is fully closed. There is a reduction in the transverse flexion strength as the arms are abducted and elbows straightened, which tends to result in a decreasing force available from the user where the force required to cut the object is increasing.
Accordingly, it would be desirable to provide a hand-operated cutting tool, such as a lopper, having a variable leverage mechanism that provides a variable mechanical advantage throughout the cutting stroke, such that the mechanical advantage increases and decreases as the amount of force required throughout the cutting stroke to cut an object increases and decreases, so that the force applied by a user to the cutting tool throughout the cutting stroke remains relatively constant.